A look at the highs and lows of weather around the world.

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More or Fewer Tornadoes?

The round of violent tornadoes early this week across the South raises the following question. Is our changing climate affecting tornadoes? The two major forces which create favorable environments for tornadoes are atmospheric instability and wind shear. Global climate change models have always indicated that a warming atmosphere will have more instability but less wind shear, suggesting the two would balance each other out. But global climate models are generalized models and have only suggested how these two elements would change in general. New research suggests that wind shear will decrease overall but conditions of high wind shear may increase particularly on the days of high instability. In other words, we might have fewer tornado days but an increase in the number of occasions with a high concentration of tornadoes. This is actually borne out in recent years as records have been set for the most and also the fewest number of tornadoes in a year. Meteorologist John Wheeler